Liquid storage tank



Oct. 3, 1944. H. HAMMEREN 2,359,416

LIQUID STORAGE TANK Filed March 3l, 1942 4 Sheets-Shea?l l Oct. 3, 1944. H HAMMEREN 2,359,416

LIQUID STORAGE TANK Filed March .'51, 1942 4 sheets-sheet 2 Oct. 3, 1944.

H. HAMMEREN LIQUID STORAGE TANK Filed March 3l, 1942 4 Sheets-Sheet 5 OCE. 3, 1944. H HAMMEREN 2,359,416

LIQUID STORAGE TANK Fil-ed March 5l, 1942 4 Sheets-Sheet 4 'mv 1m 1, lilll .m

4145 4f? jfl Patented Oct. 3, 1944 LIQUID STORAGE TANK Hans Hammcren, Bethlehem, Pa., assignor to Bethlehem Steel Company, a corporation oi Pennsylvania Application March 31, 1942, Serial No. 437,011 l 12 Claims.

My invention relates to storage tanks and more particularly to liquid storage tanks of the type provided with a movable roof or deck which iioats upon and is supported -by the liquid in the tank.

Liquid storage tanks can, of course, be made in almost any conceivable size, the chief limiting factors being the required capacity and permissible cost. American Petroleum Institute standard specifications for steel oil tanks, for instance, cover the wide range of containers from feet in diameter and 6 feet high, holding about 84 barrels, to the diameter of 220 feet and height of 40 feet, with total rated capacity of 270,820 barrels.

Tanks which are used for the storage ofl highly volatile and inilammable contents such as oil or gasoline and which are filled and emptied a number of times a year, or tanks Where fire protection is of prime importance, are customarily provided with floating roofs or decks for reducing the risk of re and the loss by evaporation as much as possible.

Such roofs must be strong, stable and buoyant, and should be easily constructed. 'I'hey must be well and quickly drained, and the draining means should not introduce any side-pull which might set up damaging friction between .the roof and the sides oi' the tank. They should permit the retention of rain-water, in the amount desired to cool the roof in summer, and for the same reason, i. e., the lessening of evaporation, as much of the tank area as possible should be covered by the roof.

Therefore, one object of my invention is a tank provided with a stable and sturdy floating roof of great strength and horizontal stiffness which is readily assembled by welding.

Another object is a roof which permits the retention of rain-water, when desired for cooling, without danger to the stability of the roof.

Another object is a roof which covers substantially the entire tank area.

Another object is a roof, on which thewater can not shift to one side, which would cause the roof to tilt and wedge within the tank.

Another object is to arrange the pontoons in such a way. that they easily can be subdivided into so many water tight compartments as to make the roof for all practical purposes unsinkable.

Another obiect is to subdivide and support the water carrying deck in such a way that the stresses in the deck and the bottom of the pontoons are Another object is an arrangement of pontoons, which makes all the fittings on the roof, which from time to time have to be inspected and adjusted, easily accessible from the pontoons, this feature being of particular importance when there is Water on the deck.

Another object is an arrangement whereby the radial pontoons can be utilized as direct support for a track carrying the lower end of a rolling ladder across the roof.

Another object is to make all the pontoons so small that they can be easily shop fabricated.

Another object is to give the deck a permanent slope toward the center which permits stability and complete drainage of the roof.

Another object is a roof drain of the folding joint type so designed and constructed that the weight of the drain will notexert excessive side thrllst on the roof toward the side wall of the tan Still another object is a siphon drain which may be used in lieu of the folding-joint type where desired.

Other objects, advantages and purposes of my invention will appear hereinafter.

Having thus given a general description of the objects of my invention, I shall now in order to make the same more clear refer to the annexed four sheets of drawings forming a part of this specification and in which like characters of reference indicate like parts:

Figure l is a top plan View of a preferred form of the oating roof of my invention, equipped with an annular pontoon and six radial pontoons subdivided into six separate compartments and open center drain, for a large oil or gasoline tank or the like.

Fig. 2 is a vertical section of said roof tank on the center line 2-2 of Fig. l.

Fig. 3 is a detail section on the line 3-3 of Fig. 1. j

Fig. 4 ris a top plan view of a floating roof similar to that in Fig. 1 but `equipped with an annular pontoon and four radial pontoons for a somewhat smaller tank.

Fig. 5 is a vertical section of said roof taken on the center line 5-5 of Fig. 4.

Fig. 6 is a. detail section on the line 6-6 of Fig. 4.

Fig. '7 is a vertical section of the complete tank showing floating roof and drainage pipe assembly diagrammatically.

Fig. 8 is a top plan view of the drainage pipe assembly straightened out to show its construction.

Fig. 9 is a side view, partly in section, of the swing joints connecting the several segments of the drainage pipe assembly.

Fig. 10 is a section taken on the line Ill- I0 of Fig. 9, and showing the swing Joint from the front.

Fig. 11 is a top plan detail view of an alternative central portion for the iloating roof of the large six radial pontoon type.

Fig. 12 is a horizontal detail section of the alternative central portion taken on the line I2-I2 of Fig. 13.

Fig. 13 is a vertical detail section taken on the line I3-I3 of Fig. 11.

Fig. 14 is a top plan detail view of an alternative central portion for the floating roof of the smaller four radial pontoon type.

Fig. 15 is a vertical section of said central portion taken on the line |5-I5 of Fig. 14.

Fig. 16 is a side view, partly in section, of the siphon drain shown in Fig. 14.

Referring now to the various characters of reference on the drawings. and considering rst a oating roof of the type shown in Figs. 1 to 3,

inclusive, which is designed for a moderately large tank, the numeral I indicates the deck, made of relatively thin welded steel plates and sloping for drainage to the center, 2 a ilat-bottomed segmental annular pontoon having an inwardly sloping tofp encircling the outer upper edge and provided with integral dependent rim 3, 4 a manhole in the deck for cleaning the tank when empty or performing other tasks inside, and 5 the emergency overflow drains. The elongated hollow radial pontoons 6, which project above the deck I, are box-shaped and substantially rectangular in cross-section, and may be of any convenient number, but for a large tank six such pontoons, as shown in Figs. 1 to 3, will aiord a. practical maximum of buoyancy and stability combined with ease of construction. Said annular and radial pontoons are also provided with access manholes 1, equipped with covers 8 having handles 9 for easy removal. The radial pontoons 6 continue outwardly to the periphery of the roof to form individual liquid tight compartments in the annular pontoon, but do not extend inwardly to the center of the deck I in this construction, the center being left partly open at the top with a hexagonal opening above plug drain I and strengthened by dependent welded ring shaped flange II and upper center plates I2 welded to upper center ring shaped baille'plate I3 to which said radial pontoons 6 are attached and terminate. Said upper center ring I3 is perforated with drain holes I4 adjacent the deck between ribs I and radial pontoons 6 and constitutes in eiect a sump or well.

The roof shown in Figs. 4 to 6, inclusive, is substantially the same in priniciple, but with four instead of six radial pontoons and is designed and modified accordingly for best use in smaller tanks. Like parts are identiiied by like numerals, but the annular pontoon I6 of this construction is made in fewer segments, and radial pontoons I1 are closed at their inner ends by end plates I8 of a substantially quadrangular box-shaped sump or well I9 strengthened by bottom flanges 20 and having drainage holes 2| between the radial pontoons, which sump is open at the top except for bracing ribs 22 and flanged border plates 23 which outline the rectangular central opening.

Both types of roof have in the exact center a drain pipe 24, into which a short section of pipe 25 may be threaded when it is desired to retain water on the roof for cooling and the like; Said drain, pipe may be joined to the drainage outlet by any conventional type of exible hose of suitable material, which in the case of tanks for gasoline or the like may be made of or covered with any of the petroleum resistant synthetic rubbers such as neoprene, for instance.

An alternative arrangement for drainag which has advantages in permanence and avoidance of side pull, is shown diagrammatically In Fig. 7. This is applicable to either of the foregoing types of roof, and in general to any floating roof with central drainage, here designated by the numeral 26. Conventional side guides and sealing means are not shown, but may obviously be of any of the many designs famlliarin the art. The same is true of roof supports, which for clearness are omitted from the drawing, but are the simple standard props, of angle iron or the like, which when the tank is low or emptied of contents will support the roof about ilve feet above the tank bottom 21.

The construction consists of three swingable pipes-an upper short piece 28, a middle long piece 29, and a lower short piece 30. Swing couplings 3|, as shown in detail in Figs. 9 and l0, each braced by a welded bracket 32 of rolled sections, connect the separate sections of pipe together, as shown in Fig. 8, which also illustrates a modified swing joint 33 by which the whole system is attached at the top to check valve 34 and sump 35 in the center of roof 26.

When the roof is at lowest point 36, i. e., about ve feet above the bottom 21, in Fig. '1, the middie long piece of pipe 29 is supported on a "horse" or similar support 31 about three feet above said bottom, and is in balance about this support. The pipe assembly can therefore be swung into position 38, as the amount of nuid in the tank increases, without any side pull on the roof. After the assembly has passed said position 38, and reached positions 39 and 40, the angle -between the two upper pieces of pipe is so large that the side pull will not be excessive. A smaller open distance between roof and bottom, say three feet, would call for the use of a number of short pipes.

Figs. 11 to 15, inclusive, illustrate floating roofs of the closed center type. In Figs, 11 to 13 the roof has six radial pontoons 4I which are joined together at the center by closed central pipe 42 and top plates 43. Drainage is by plug drains 44, and the deck spaces between the pontoons are Joined by open pipes 45 through the pontoons and adjacent the bottom thereof. 'Ihe roof center shown in Figs. 14 and 15 is likewise enclosed. The four radial pontoons 46 are similarly pierced by drainage pipes 41, and plug drains 48 furnish part of the drainage.

The siphon drains 49 which also appear in Fig. 14 are more fully shown in Fig. 16. Flat bottomed water-pan 50, of sheet metal or the like, opens onto a short supporting length of pipe 5I, which connects by elbow 52, short horizontal pipe '53 and 90 elbow 54 t0 long vertical pipe 55, which latter is threaded into coupling 56 welded to and extending slightly above the surface of the deck to prevent dirt from entering and stopping the drain.

The action of the siphon drain is as follows. Before filling the tank, water is poured into water pan 50 until it reaches the level of the rim. Thereby the water will come to a corresponding level in pipe 55. As an immiscible liquid, e. g.,-

astaaic gasoline, comes into the tank it will rise above the level of the water pan and exert additional pressure, forcing down the water in pan 50 and causing a rise in the level of the water in the pipe i5. Additional water is added at the top of pipe 55, until when the tank is filled the water in the pan 50 stands at the rim thereof and the water in pipe -55 is at the top of coupling 5l. It is apparent that the length of pipe 55 must vary, to attain this result, according to the actual specific gravity of the liquid stored in the tank. Water on the roof above the level of the coupling 56 will cause the water in the pan i0 to overflow, and being heavier than oil or gasoline it will sink to the bottom of the tank where it may be removed by a conventional sump connected to a drainage pipe (not shown). Nipple 51 will allow additional water for insulating and cooling purposes to be retained on the deck, and cap 58 may be screwed onto said nipple if the drain is to be put out of service.

Although I have shown and described my'invention in considerable detail, I do not wish it to 'be limited to the exact construction shown and described. `but I may use such substitutions, modications or equivalents thereof, as are embraced within the scope and spirit of my invention, or as are pointed out in the appended claims. 'The siphon and other drains shown, for example, may obviously be increased or decreased in number to accord with the average amount of rainfall of the particular locality where the tank is to be erected, or they may be placed in the center or other portions of the roof with suitable modifications.

Having thus described my invention what I claim as new and desire to secure by Letters Patentis:

1. The combination with a liquid storage tank, of a floating roof comprising a circular deck, an annular pontoon encircling the periphery of the deck like the rim of a wheel, closed bottom radial pontoons oblong in horizontal cross-section andof uniform vertical cross-section through-l out their length spaced apart and arranged like the spokes of a Wheel on the deck, and means of draining the deck as required.

2. The combination with a liquid storage tank, of a floating roof comprising a relatively flexible circular deck, a flat-bottomed annular pontoon forming a rigid rim for the circumferential portion of said flexible deck, and elongated closed bottom box-shaped pontoons of uniform crosssection throughout their length radiating from the center of the deck and further bracing and making rigid the deck.

3. 'Ihe combination with a liquid storage tank, of a floating roof comprising a deck sloped toward the center made of relatively thin metal plates, drainage means at the center of the deck, upright baille plates enclosingthe drainage means perforated to allow passage of the liquid to be drained, al segmental annular pontoon circumferentially disposed around said deck, and radially extending pontoons of uniform Vertical cross-section throughout their length symmetrically disposed between and connecting the annular pontoon and the baille plates.

4. The combination with a liquid storage tank, of a floating roof comprising a circular deck, an annular pontoon extending upwardly around the rim of the deck, upwardly extending bracing members at the center of the deck, and closed bottom pontoons of uniform rectangular crosssection throughout their length radiating outwardly from the bracing members to the annular pontoon. i

5. The combination with a. liquid storage tank, of a floating roof comprising a deck depressed toward the center, an annular pontoon extending upwardly around the rim of the deck, an upwardly extending ringlike member in the center of the deck, radial elongated box-like pontoons of uniform cross-section throughout their length connecting the ringlike member and the annular pontoon, and means for leading water from the deck to the exterior of the tank.

6. The combination with a liquid storage tank, of a floating roof supported by the liquid in the tank, having a deck with an annular pontoon and a downwardly depending flange about the edge of the deck, a plurality of spaced radial closed bottom pontoons uniform in cross-section throughout their length tangent to the annular pontoon on the deck, said deck having a depressed point at the center with a sump located at the depressed point, means for permitting drainage of surface Water to the sump, and means for draining the water from the sump.

7. The combination with a liquid storage tank, of a floating roof comprising a. deck depressed for drainage toward the center, an annular pontoon circumferentially about the deck, a. plurality of converging elongated radial pontoons uniform cross-sectionally throughout their length dividing the deck into open sectors and forming a closed center, drain pipes adjacent the deck through said radial pontoons and connecting the deck sectors, and means for draining said deck sectors.

8. The combination with a liquid storage tank, of a floating roof comprising a deck depressed toward the center, an annular pontoon about the perimeter of said deck, a central box-like well or o sump having regularly spaced perforations for permitting drainage thereinto, a central pipe for conducting drains therefrom, and long evenly spaced radial pontoons of closed box shape and uniform cross-section throughout their length between said annular pontoon and the well or sump.

9. The combination with a. liquid storage tank, of a. floating roof comprising a deck depressed toward the center, an annular pontoon encircling said deck, a central well or sump for drainage comprising an upright metal ring with perforations permitting drainage to the center, a drain pipe in the center, and radial pontoons crosssectionally uniform throughout their length spaced between the perforations and welded to the annular pontoons and the upright metal ring respectively.

10. The combination with a liquid storage tank, of a. floating roof comprising an interiorly sloping deck, an annular pontoon about the periphery of said deck, and a sump for drainage comprising a centrally disposed upright ring provided with perforations adjacent the deck permitting drainage to the center, a drain pipe in the center for removing excess fluid, welded cover plates defining a hexagonal opening above the drain pipe, welded ribs for supporting the cover plates, a dependent ring shaped ange for bracing the bottom of the sump, and radial oblong pontoons connecting the anular pontoon and the Sump.

11. The combination with a liquid storage tank, of a floating roof comprising a deck depressed toward the center, drainage means at the center of the deck, an annular pontoon extending up- .continuing inwardly along the center lines of the radial pontoons, a vent for waste gases, and upper fitted border plates welded to ribs and baille plates and defining a central opening for the escape of Waste gases.

12. The combination with a liquid storage tank of a floating roof comprising 'a deck plate portion dished suiilciently to permit drainage to the center of the roof, an annular pontoon at the pef riphery of the roof positioned entirely above the deck plate portion, the top plate of the annulax` pontoon being sloped inwardly and the bottom plate of the annular pontoon being a continuation of the deck plate portion but being flat in a planeparallel to the bottom of the tank, a ring constituting the `periphery of the roo! extend- 4ing downwardly below the deck plate portion,

oblong closed pontoons ot substantially rectangular cross-section extending radially from a point adjacent the center to the periphery of the root and projecting entirely above the face of the deck plate portion, baille plates positoned between the center and the edge of the roof and extending 

